Guard Monitoring System (GMS)

With the installation of the Digital Train Radio System, a requirement was to enable the guard at the rear of the train to be able to listen in on the conversations the driver has with the train controller. As there were no free train lines available for this purpose, the solution was to send the audio on the existing audio train line pair by a 200 kHz FM modulated carrier.

Main features:
The 200 kHz carrier is derived from the microcontroller and modulated/demodulated with phased locked loops.

Outcome of the project:
260 units were built and are now installed on the Tangara trains

GMS circuit board
GMS block diagram